The objectives of this research project are to: 1. Determine the frequency distribution of calcium excretion for a random sample of the adult population. 2. Delineate the risk-factors for urolithiasis. 3. Examine specifically "hypercalciuria" in a group of patients with urolithiasis and search for possible familial aggregation of this characteristic. Methods to achieve the objectives are: 1. a survey to measure calcium excretion in a representative and randomly drawn sample of the community. 2. a case-control epidemiologic study comparing urolithiasis patients to controls on a variety of characteristics as excretion of calcium urate, occupation, drug ingestion and family history. 3. Examine family members of urolithiasis patients and controls for the presence of familial aggregation of "hypercalciuria". Finally, if a population of "hypercalciuric" persons is discovered in the community survey, the feasiblity of planning and conducting a cohort study (prospective) of "hypercalciuric" and normocalciuric groups for their subsequent incidence of urolithiasis will be examined. The work proposed should significantly enlarge our understanding of the role of calcium metabolism in the etiology of urolithiasis and will help elucidate the importance of genetic and environmental influences upon the development of this disease. Further, a search for risk-factors for urolithiasis will be made and, if successful, preventive measures may be suggested as a result of this work.